Plasma method and apparatus for generating energy



United States Patent 3,361,634 PLASMA METHOD AND APPARATUS FORGENERATING ENERGY Louis D. Smullin, Watertown, Mass., assignor to LIPHA,Lyonnaise Industrielle Pharmaceutique, a corporation of FranceContinuation of application Ser. No. 238,834, Nov. 16, 1962. Thisapplication Mar. 18, 1966, Ser. No. 535,612

20 Claims. (Cl. 1763) This application is a continuation of applicationSer. No. 238,834, filed Nov. 16, 1962, now abandoned.

The present invention relates to methods of and apparatus for generatingenergy, and, more particularly, to the generation of energy with the aidof gaseous plasma.

Numerous proposals have been offered in recent years for the generationof energy in gaseous-plasma systems and, in particular, in thermonuclearfusion systems wherein the combination of light elements at the low endof the periodic table, such as hydrogen, deuterium and tritium, iseffected to form heavier and more tightly bound nuclei as of helium,while releasing large quantities of energy in so doing. A summary ofthese proposals, together with the limitations thereof in terms of thedevelopment of stability in the confining of the high-temperature plasmato allow substantial fusion and the subsequent harnessing and conversionof the released energy for power purposes, is set forth, for example, inProject SherwoodThe U.S. Program in Controlled Fusion, by A. S. Bishop,Addison-Wesley Publishing Company, 1958.

An object of the present invention, accordingly, is to provide a new andimproved method of and apparatus for generating energy in gaseous-plasmasystems that shall provide improved stability, control andenergy-harnessing results.

A further object is to provide a novel thermo-nuclearfusionenergy-generating apparatus.

Other and further objects will be explained hereinafter and will be moreparticularly pointed out in the appended claims. In summary, however,the invention contemplates apparatus for producing energy having, incombination, a container, means for generating gaseous plasma within thecontainer, means for confining the plasma as a body floating within apredetermined spatial region of the container displaced from the wallsthereof, including electron voltage and current controlling means forinjecting an electron beam into the said spatial region and the floatingplasma therein, the last-named means being adjusted not only to providea beam voltage of the order of at least hundreds of thousands of voltsto produce sufficient energy to excite the ions of the plasma to a hightemperature corresponding to thousands of electron volts but also toprovide an electron beam current of value such that the ratio of thenumber of electrons in the beam to the number of electrons in the plasmais sufliciently large to cause an avalanche of sustained oscillationsbetween the plasma and the electrons, and means for extracting energyfrom the plasma at a region displaced from the said spatial region.Preferred constructional details and process steps are hereinafter setforth.

The invention will now be described in connection with the accompanyingdrawing, FIG. 1 of which is a schematic longitudinal section of anembodiment of the invention; and

FIG. 2 is a similar view of a preferred form.

Basically, as before explained, the invention contemplates a novel kindof coupling and interaction between an electron beam and a plasma. Thebeam of electrons injected into the plasma will, by one of several modesof interaction with the plasma, cause oscillations to be excited. Theseoscillations are usually in the neighbor- 3,361,634 Patented Jan. 2,1968 hood of some characteristic frequency such as the electron plasmafrequency, the electron or ion cyclotron frequencies, or the ion plasmafrequency. Alternating electromagnetic fields are generated, and theions and/or electrons are given a corresponding oscillatory or gyratingmotion at the same frequencies. The oscillatory kinetic energy impartedto the ions or electrons is derived from the DC. kinetic energy of theinjected electron beam. If the oscillation is strong enough, the kineticoscillation energy may be hundreds or thousands of volts or more. Astime goes on, this coherent or organized motion is randomized by theoccasional collisions between particles. In the applicants experiments,for example, random electron energies of thousands of volts have beenproduced.

The object, of course, is to heat the ions of the plasma. This might bedone in either of two ways: first, heat the electrons and then allow theions to be heated by collisions; or secondly, to excite the ions intooscillation directly. Oscillation frequencies of ions are relativelylow, the order of megacycles/second or less. In order to transform thebeam electrons and DC. kinetic energy into ion oscillations, thefrequency of collision of the beam electrons must be small compared withthe ion oscillation frequency. At typical operating pressures of 10* to10- mm. Hg of hydrogen or deuterium, for example, and with beam voltagesof, for example, about 100,000 to 250,000 volts, this condition isautomatically satisfied.

The coupling between the electron beam and the plasma, and thus the rateof power transfer into oscillation energy, is proportional to the ratioof beam-electrondensity to the plasma electron density; and to the ratioof DC. beam voltage to plasma temperature, expressed in electron volts.Thus, the object is to inject a very dense, high-voltage beam into theplasma.

The system of FIG. 1 is adapted for utilizing the injected electron beameither to transfer power to a plasma that has been ionized and elevatedto a high temperature by auxiliary means (which is not useful for veryhigh power systems where ionizing electrodes and the like may vaporize),or to employ the electron beam itself first to heat the plasma and thento transfer power thereto to produce a novel runaway avalanche ofsustained oscillations between the ions of the plasma and the electrons.

Considering the first possibility, a container or reactor 1 ofpreferably nuclear-and-atomic-radiation impermeable material, that is,however, magnetic-field permeable, as of stainless steel or the like, isevacuated at a predetermined pressure through connection to a vacuumsystem, schematically shown at 3. Into the container 1, a gaseousmedium, as of hydrogen, deuterium, tritium and the like, or mixturesthereof, is fed through a valve V from a supply source 5. The gaseousmedium is ionized by auxiliary means into a plasma state in the regionI, labelled Plasma, that, in the particular embodiment shown, extendsbetween a pair of annular anode electrodes A, A connected to thepositive terminal of a high-voltage power supply 7 of, for example, thecontinuous or pulsed variety. The negative terminal of the power supply7 is connected, upon closure of switch S, to a pair of cathodes C and C,respectively cooperative with the anodes A and A, and the latter cathodeC of which is apertured at 9 for a reason later made apparent. The highvoltage applied between the anodes A and A and the correspondingcathodes C and C' may be produced by discharges from a bank ofperiodically charged capacitors, schematically represented at 11, andwhich may assume the form described, for example, at pages 144-5 of thesaid Bishop book, or the so-called P.I.G. (Penning Ionization Gauge)construction described in Character- 3 istics of Electric Discharge inMagnetic Fields, chapter 11, A. Guthrie and R. K. Wakerling, McGraw-HillBook Co., New York, 1949. In any event, the voltage applied between theanodes A, A and their respective cathodes C, C is sufficient to producea high-temperature ionized plasma at I.

In order to prevent loss of energy in striking the walls of thecontainer 1, the plasma is confined to the spatial region I as afloating body within the container 1, as by, for example, a magneticfield of the mirror type, described on pages 523 of the said Bishopbook; being illustrated as produced by external magnetic-field producingcoils 13, generating greater field strength at the larger end turns 13'thereof.

In accordance with one form of the present invention, large amounts ofenergy are transferred to the ions in the plasma by means of anappropriate electron beam. If thermonuclear fusion is desired, theplasma must be held at temperatures of the order of millions of degreeslong enough to permit a substantial portion of the gaseous nuclei toundergo fusion.

\Vhile electron beams have previously been interacted with gaseousmedia, as in traveling-wave amplifiers, klystrons and the like, neithera confined fusible-gas plasma nor an electron-beam voltage and currentdensity of the order of magnitude required for the phenomenon underlyingthe present invention have been involved. To the contrary, the onlyeffect of coupling between an electron beam and the ions in such systemshas been a type of ion oscillation appearing as a modulation side-bandthat, indeed, has been characterized as an undesirable form ofdistortion that is to be minimized. In accordance with the presentinvention, on the other hand, the electronbcam induced ion oscillationspreviously described are maximized and trapped to generate ion energiesthat are the equivalent of many millions of degrees of temperature. Foran electron beam of at least one or a substantial fraction of one ormore hundreds of thousands of volts (hereinafter generally termed theorder of at least hundreds of thousands of volts) and an appropriateelectron-beam current density, for example, ion energies of -20kilovolts and more may be produced; and with an axial magnetic field oftens of thousands of gauss, confinement of the high-velocity ions tosmall radii results in adequate trapping in the beam. Electron-beampower of from at least a substantial fraction of a megawatt to manymegawatts, hereinafter generically embraced by the phrase substantiallymegawatts, are employed.

Specifically, in the embodiment shown in FIG. 1, a high-power electronbeam is produced in a hot-cathode electron gun 2 that is shownmagnetically shielded from the plasma spatial region I by a magneticallyshielding housing 23, apertured at 15 to permit the projection of theelectron beam through the aperture 9 in the cathode C and into theplasma 1. The electrodes of the gun 2 (cathode 2', forming anode 2".etc.) are shown connected to an electron-beam voltage supply 17 that, inaccordance with the invention, is adjustable to produce the desiredelectron-beam voltage and current necessary for the phenomenonunderlying the invention.

This high-power beam is illustrated in FIG. 1 as generated in alower-pressure vacuum than the degree of vacuum within the container 1,as by the differential evacuating system 3'. The shield 23, moreover,reduces the field at the electron-gun cathode 2 to a value much lessthan that at the region 15 of beam emergence, in order to provide adense electron beam that is convergent, so as to permit focusing of beamcurrents of the order of up to hundreds of amperes per squarecentimeter, with cathode current densities held below about ten amperesper square centimeter, substantially upon the axis of the plasma at theregion I. The field at the electron gun may have to be reduced by abucking coil 19, should the iron of the shield 23 tend to saturate.

In the case of the mirrow-type plasma-confining field, before discussed,the windings 13, as of copper, or, if

A desired, super-conducting conductors maintained in a liquid helium orother refrigerant, may generate a field of the order of ten thousandgauss, and greater, to provide effective floating-body confinement andtrapping of the plasma, with a low intermediate field-density and highend field-density.

So-called electron magnetron-injection guns, as shown in FIG. 2, mayalso be employed to produce a hollow electron beam within strongmirror-type fields; or auxiliary gas-discharge systems, not shown, mayserve as the electron beam source. In all cases, however, as shown inFIGS. 1 and 2, the electron-beam gun is located in a region of intensemagnetic field where it is relatively isolated from the main plasmaregion 1.

Other types of confining systems may also be employed such as, forexample, the capacitive-discharge-produced Scylla-type transientmagnetic field described, for example, on page 147 of the said Bishopbook. In the case of such a transient field, the electron gun 2 wouldproject or inject electrons during the first half-wave of half-cycle ofthe discharge.

The applicants experiments have demonstrated that, as before mentioned,auxiliary plasma ionizing apparatus, such as A, A, C, C of FIG. 1, isnot needed nor, indeed, feasible with extremely high-power devices; butthat an appropriate hot electron beam may be used both to bring the ionsup to high temperature and to exchange power therewith to set ott anavalanche that results in novel sustained plasma-electron oscillations.

With the switch S of FIG. 1 opened (and, indeed, elements A, A, C, C,etc. removed, as in FIG. 2), if one adjusts the electron-beam voltage at17 to the order of at least hundreds of thousands of volts, sufiicientenergy can be produced to excite the ions of the plasma directly fromthe electron beam to a high temperature corresponding to many thousandsof electron volts. The electron-beam current must also be adjusted at 17and by gun aperture size, etc., in weil-known manner, to a rathercritical degree; namely, the ratio of the electron density in the beamto the density of electrons in the plasma must be sufficiently high thatan avalanche effect is produced resulting in sustained oscillationsbetween the plasma and the electrons. This avalanche and novel strongoscillation effect is readily detected, but has apparently previouslyescaped notice because, in prior art systems, all of the necessary andsufficient conditions above described were not fulfilled. A drop inperveance [electron beam current/(electron beam voltage) from the orderof at least 10- by a factor of one-half, for example, has been found tobe sufficient for the phenomenon of the present invention not to takeplace in experimental structures of the type shown in FIG. 1. If thepeak of the energy of oscillations is less than the ionization potentialof the gas, only elastic collisions and scatter will occur, but noionization of the above character. To get a runaway or avalanchedischarge the oscillation energy must be made considerably greater thanthe ionization potential of the gas. With the electron beam itselfgenerating a very highly ionized plasma by first building up a weakplasma through ordinary collisions with the neutral gas and theninteracting with the plasma to produce oscillations, the plasmaelectrons acquire enough energy to take part in the ionization process,and the density grows exponentially with time. Thus, in accordance withthe discoveries underlying the invention, the entire process ofproducing and heating the plasma can be performed by the proper electronbeam alone.

For thermonuclear purposes, adjustment of the parameters of the electrongun controls 17 to provide an electron-beam voltage of the order of halfa million volts and an electron-beam current of the order of 300-500amperes may, for example, be effected.

Whether the present invention is used for thermonuclear fusion heatgeneration or energy generation of lesser magnitude, it is necessary toharness and couple out the generated heat energy. This may be done byemploying the heat energy released and radiated from theelectronbeam-interacted plasma at the walls of the container 1, whichare displaced from the confined floating plasma spatial region 1. Thus,preferably externally disposed coolant pipes 21 may surround the wallsof the container opposite the region I for there absorbing andtransferring the energy radiated from the plasma. If desired,furthermore, moderator blankets, not shown, may surround the containerto prevent neutron escape.

The energy generation by the process herein described may also be usedfor other purposes, as for propulsion. In such event, the energy of theelectron-beam-interacted plasma may, for example, be permitted to beexpelled, as at 3".

Further modifications will also occur to those skilled in the art andall such are considered to fall Within the scope and spirit of theinvention as defined in the following claims.

What is claimed is:

1. A method of the character described that comprises generating agaseous plasma including electrons, magnetically confining the plasma asa floating body within a predetermined spatial region, injecting a densehigh-voltage electron beam into the said spatial region and thus intothe plasma, adjusting the electron beam voltage to the order of at leasthundreds of thousands of volts, adjusting the current density of theelectron-beam such that the ratio of the number of electrons in the beamto the number of electrons in the plasma is sufiiciently large, namelyto provide a ratio of electron beam current to the three-halfs power ofthe electron beam voltage of the order of at least to cause an avalancheof sustained oscillations between the plasma and the electrons, with theelectron-beam collision frequency small compared with the electron-beamcollision frequency small compared with the frequency of the saidoscillations, and extracting energy of the plasma at a region displacedfrom the said spatial region.

2. A method as claimed in claim 1 and in which the gaseous plasma isionized and heated separately from the said injecting of the electronbeam.

3. A method as claimed in claim 1 and in which the gas is a fusible gasselected from the group of gases consisting of hydrogen, deuterium andtritium and in which the same is substantially fully ionized.

4. A method as claimed in claim 1 and in which the said spatial region,apart from the electron beam and gaseous plasma, is evacuated.

5. A method as claimed in claim 1 and in which the injected electronbeam is generated within a further region evacuated to a differentdegree of vacuum than the said spatial region.

6. A method as claimed in claim 1 and in which the injected electronbeam is generated within a further region magnetically shielded from thesaid spatial region.

7. A method as claimed in claim 1 and in which the injected beam isgenerated in a further region substantially isolated from the saidplasma region.

8. A thermonuclear method as claimed in claim 1 and in which 'the saidgas is a fusible gas, the said high voltage of the electron beam isadjusted to the order of at least about 500,000 volts, and the said beamcurrent is adjusted to the order of at least from about 300 to about 500amperes.

9. A method as claimed in claim 1 and in which the energy extracting iseffected by absorbing heat energy from the ionized plasma over a regionsurrounding the said spatial region.

10. A method as claimed in claim 1 and in which the energy extracting iseffected by expelling energy of the ionized plasma.

11. A method as claimed in claim 1 and in which the magnetic confiningis effected by relatively intense magnetic fields at the ends of theplasma and a relatively weaker field intermediate the same.

12. A method as claimed in claim 11 and in which the injected electronbeam is generated at a further region disposed in one of the saidintense end magnetic fields.

13. Apparatus for producing energy having, in combination, a container,means for generating gaseous plasma within the container,magnetic-field-producing means for confining the plasma as a bodyfloating Within a predetermined spatial region of the containerdisplaced from the walls thereof, means for generating and injecting adense high-voltage electron beam into the said spatial region and thefloating plasma therein, the last-named means producing an electron-beamvoltage of the order of at least hundreds of thousands of volts and anelectronbeam of current density such that the ratio of the number ofelectrons in the beam to the number of electrons in the plasma issufficiently large, namely to provide a ratio of electron beam currentto the three-halts power of the electron beam voltage of the order of atleast l0* to cause an avalanche of sustained oscillations between theplasma and the electrons, and means for extracting energy from theplasma at a region displaced from the said spatial region.

14. Apparatus as claimed in claim 13, and in which the magnetic-field isof the order of ten thousand gauss and greater, and the said last-namedmeans produces an electron-beam power of at least the order ofsubstantially megawatts.

15. Apparatus as claimed in claim 13 and in which the container and theelectron-beam generating means are evacuated to different degrees.

16. Apparatus as claimed in claim 13 and in which there is providedmeans for isolating the electron-beam generating means from the saidspatial region.

17. Apparatus as claimed in claim 13, and in which the container ismetal-walled, the means for generating the electron beam is providedwith shield means for shielding the generating means from the saidspatial region, and further comprising means for producing a subsidiaryfield for reducing the field at the electron-beam generating means toprevent saturation of the shielding means, the electron-beam collisionfrequency being small compared with the frequency of the saidoscillations.

18. Apparatus as claimed in claim 16 and in which the electron beamproduces both ionization and heating of the plasma and transfer of powerthereto for the said sustained oscillations, with the electron-beamcollision frequency small compared with the frequency of the saidoscillations.

19. Apparatus as claimed in claim 16 and in which the extracting meanscomprises means for ejecting energy from the said plasma.

20. Apparatus as claimed in claim 17 and in which the gaseous plasmacomprises a fusible gas.

No references cited.

REUBEN EPSTEIN, Primary Examiner.

1. A METHOD OF THE CHARACTER DESCRIBED THAT COMPRISES GENERATING AGASEOUS PLASMA INCLUDING ELECTRONS, MAGNETICALLY CONFINING THE PLASMA ASA FLOATING BODY WITHIN A PREDETERMINED SPATIAL REGION, INJECTING A DENSEHIGH-VOLTAGE ELECTRON BEAM INTO THE SAID SPATIAL REGION AND THUS INTOTHE PLASMA, ADJUSTING THE ELECTRON BEAM VOLTAGE TO THE ORDER OF AT LEASTHUNDREDS OF THOUSANDS OF VOLTS, ADJUSTING THE CURRENT DENSITY OF THEELECTRON-BEAM SUCH THAT THE RATIO OF THE NUMBER OF ELECTRONS IN THE BEAMTO THE NUMBER OF ELECTRONS IN THE PLASMA IS SUFFICIENTLY LARGE, NAMELYTO PROVIDE A RATIO OF ELECTRON BEAM CURRENT TO THE THREE-HALFS POWER OFTHE ELECTRON BEAM VOLTAGE OF THE ORDER OF AT LEAST 10**-6, TO CAUSE ANAVALANCHE OF SUSTAINED OSCILLATIONS BETWEEN THE PLASMA AND THEELECTRONS, WITH THE ELECTRON-BEAM COLLISION FREQUENCY SMALL COMPAREDWITH THE ELECTRON-BEAM COLLISION FREQUENCY SMALL COMPARED WITH THEFREQUENCY OF THE SAID OSCILLATIONS, AND EXTRACTING ENERGY OF THE PLASMAAT A REGION DISPLACED FROM THE SAID SPATIAL REGION.